286 A. L. MELANDER. 



Fourth vein reaching the margin of the wing; thorax almost always con- 

 spicuously vittate ; eyes of the males separated (as far as known with 

 very few exceptions) 39- 



32. Wings spotted with brown, anterior branch of the third vein perpendicu- 



lar 33. 



Wings unspotted, first submarginal cell open 34. 



33. First submarginal cell generally closed ; fourth vein not forked. 



clausa Coquillett. 

 First submarginal cell open ; the shortened fourth vein furcate. 



spiloptera Wiedemann. 



34. Third antennal joint five times as long us wide, style minute. 



triangiila Coquillett. 

 Thirt joint shorter, style comparatively longer 35. 



35. Second submarginal cell wider than the first posterior cell...<iistaiis Loew. 

 Second submarginal cell subequal in width to the first posterior 36. 



36. Wings dark brown 37. 



Wings but little infumated 38. 



37. Knob of halteres yellowish above; eastern species labiata Loew. 



Halteres black, with paler pedicel ; Mexican species.. .tolipennis Bellardi. 



38. Joints of the male front tarsi globose and provided with long hairs. 



aseina sp. uov. 

 Joints of the tarsi slender, not long-hairy. 



dolorosa Wheeler et Melander. 



39. Legs, at least femora, nearly black or wholly black 40. 



Legs, at least in large part, yellowish or reddish 55. 



40. Abdomen wholly black 41. 



Abdomen yellow at the base; legs of female feathered. 



pegasus Osten Sacken. 



41. Knob of halteres pale 42. 



Knob of halteres at least infuscated 49. 



42. Eyes of male contiguous; thorax wholly shining Itevigata Loew. 



Eyes of male separated ; thorax vittate 43. 



43. Venter of male with a subapical process; legs simple; thorax and abdomen 



somewhat shining 44. 



Abdomen of male simple; male hind legs with processes; thorax opaque. ...47. 



44. Ventral process of fifth abdominal segment of male with long hairs 45. 



Ventral process with short or no hairs 46. 



45. >Iesonotum with three shining vittse; scutellum with four bristles. 



pellueida Coquillett. 

 Mesonotum evittate ; scutellum with six or more bristles. 



fuinifla Coquillett. 



46. Ventral process with short hairs ; central filament hidden. 



Tirgata Coquillett. 

 Ventral process devoid of bristles; central filament exposed. 



infnmata Coquillett. 



47. Outer process of hind tibise of male simple; middle legs not tipped with 



many spurs 48. 



Outer process of male hind knees large, pronged ; middle tibise tipped by a 

 circle of spurs serperastrorum sp. nov. 



